30 Questions
Which type of solubility curves shows sudden changes of solubilities?
Discontinuous solubility curves
Which substance shows exceptional behavior with its solubility decreasing as temperature increases?
Ce2(SO4)3
Which compound shows a very small change in solubility from 0°C to 100°C?
NaCl
What type of solubility curve is represented by K2Cr2O7, Pb(NO3)2, and CaCl2?
Continuous solubility curve
Which compound's solubility becomes constant from 40°C onwards?
Ce2(SO4)3
What causes discontinuous solubility curves?
Combination of two or more solubility curves
What is the term used to describe the stage where increasing dilution produces no further heat change?
Infinite dilution
What happens when ionic compounds are dissolved in water?
They are dissociated into ions
What is the term for the process in which water molecules surround and interact with solute ions or molecules?
Hydration
What are the ions surrounded by water molecules called?
Hydrated ions
What determines the number of water molecules surrounding a given ion?
Ion's size
What does high charge density indicate for a small, highly charged positive ion?
High level of hydration
What property of solutions is being discussed in the text regarding the elevation of boiling point?
Boiling point elevation
Which graph is typically used to illustrate the depression of freezing point in solutions?
Line graph
Why do freezing points of solutions decrease when non-volatile solutes are added to volatile solvents?
Decrease in vapor pressure
What property of a solution is discussed when analyzing the energetics of solution?
Temperature changes
In which scenario would you use molality instead of molarity to express concentration?
When volume changes significantly with temperature
What does the mole fraction of a solute represent in an aqueous solution?
Proportion of solute particles relative to all particles
What is the formula to calculate parts per million (ppm)?
Mass of solute x 10^6 / Mass of solution
In the example provided about sea water, what is the concentration of oxygen in parts per million (ppm)?
5.65 ppm
Which unit of concentration conversion is usually done when we know the formula masses and densities of solutes or solutions?
Molality to molarity
What is the correct formula to convert molarity to molality?
Molarity = Molality / Molar mass
Which concentration unit conversion is essential for laboratory work involving fractions of acids?
Conversion from w/w percentage to molarity
In the context provided, which conversion unit is used for interconverting various concentration units?
Parts per million to molarity
What does the difference of the two freezing points provide?
Value of molar mass of solute
In the freezing point depression formula M2 = Kf 1000 W2 ∆Tf W1, what does 'M2' represent?
Molar mass of solute
What is the significance of adding a non-volatile compound to a solution in terms of its freezing point?
Lowers the freezing point
How does the presence of a solute affect the liquid range of a solution?
Expands the liquid range by raising boiling and lowering freezing points
What is the most common application mentioned for using antifreeze in an automobile radiator?
To prevent freezing in cold weather
How does Beckmann's freezing point apparatus contribute to determining properties of solutions?
By measuring freezing point depression
Study Notes
Heat of Dilution
- The heat of dilution decreases gradually, and eventually, increasing the dilution produces no further heat change.
- This occurs when there are 800-1000 moles of water to one mole of solute, a stage called infinite dilution.
- The heat of solution is expressed as: NaCl(s) + H2O → NaCl(aq) → Na+(aq) + Cl-(aq) with a ∆Hsoln = +4.98 kJ mol-1.
Hydration
- When ionic compounds are dissolved in water, they are dissociated into ions.
- Negative ions are surrounded by water molecules, with the partial positively charged hydrogen atoms of water surrounding and attracting the anions with electrostatic forces of attraction.
- Similarly, positive ions of the solute create attractions with partial negative oxygen atoms of water molecules.
- The process of water molecules surrounding and interacting with solute ions or molecules is called hydration.
- The number of water molecules surrounding a given ion depends on the size of the ions and the magnitude of its charge (charge/area).
Concentration Units
- Parts per million (ppm) is a unit used for very low concentrations of solutions, e.g., to express the impurities of substances in water.
- ppm = Mass of solute x 10^6 / Mass of solution.
Interconversion of Concentration Units
- It is possible to convert one unit of concentration into another, such as converting molarity to molality or w/w percentage.
- This conversion is done if we know the formula masses and the densities of the solutes or solutions.
Energetics of Solution
- The heat of solution can be exothermic (releasing heat) or endothermic (absorbing heat).
- The energetics of solution involve the heat of solution, which can be calculated using the heat of hydration and the lattice energy of the solute.
Solubility Curves
- Solubility curves are graphical representations of the temperature vs. solubility of a solution.
- There are two types of solubility curves: continuous and discontinuous.
- Continuous solubility curves show a gradual change in solubility with temperature, while discontinuous solubility curves show sudden changes in solubility.
Applications of Boiling Point Elevation and Freezing Point Depression
- The presence of a solute increases the liquid range of the solution by raising the boiling point and lowering the freezing point.
- This phenomenon has important applications, such as the use of antifreeze in the radiator of an automobile.
Test your understanding of calculating parts per million (ppm) of substances in solutions. Practice determining the concentration of solutes in solutions with low concentrations using the ppm formula. This quiz includes a sample calculation for better comprehension.
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